Many cleaning compositions include a thickening agent to impart a level of viscosity to the composition, and to provide increased contact time on surfaces to be cleaned. Such compositions are presently used in many applications, such as retail, industrial and institutional including grease cutters, clinging lime scale removers, shower wall cleaners, bathtub cleaners, hand sanitizing gels, disinfectant gels, hand-soaps, teat dips, coatings, stabilized enzymes, structured liquids, and the like. Traditionally, these compositions use a polymer thickening agent to impart the desired viscosity. Polymeric thickeners, e.g. starches, thicken by entanglement of the polymeric chains.
Examples of commonly used polymeric thickening agents include guar gums and derivatives thereof, cellulose derivatives, biopolymers, and the like. Water soluble polymers, particularly polysaccharide polymers, such as, for example, guar, guar derivatives, starches, and cellulosic polymers, are commercially available materials used in a variety of applications, including as ingredients in food products, personal care compositions, agricultural pesticide compositions, and compositions, such as fracturing fluids, for use in oilfield applications.
The use of polymeric thickening agents has certain drawbacks. Such thickeners can degrade under the influence of mechanical shear or chemical scission (e.g. by oxidation or hydrolysis) of the polymeric chains which results in a loss of viscosity and, thus, suspension stability. The polymeric thickening agent may leave an undesirable gel residue on a surface to be cleaned. It is also believed that the cleaning action of at least some of the active cleaning components within the composition is reduced with a consequent and marked reduction in the cleaning action required for effective cleaning and oily soil removal. While not wishing to be bound by any theory, it is believed that the polymer thickener may act as a barrier, and slows down the diffusion of at least some of the active cleaning ingredients, thereby reducing contact with the soil. Additionally, it is believed that the polymer thickener may act to dilute the active cleaning agents within the cleaning composition, thereby reducing the cleaning effectiveness.
The term “viscoelastic” refers to viscous fluids having elastic properties, i.e., the liquid at least partially returns to its original form when an applied stress is released. Thickened aqueous viscoelastic fluids have been used in hydraulic fluids in lubricant and hydraulic fracturing fluids to increase permeability in oil production.
The property of viscoelasticity in general is well known and reference is made to S. Gravsholt, Journal of Coll. And Interface Sci., 57(3), 575 (1976); Hoffmann et al., “Influence of Ionic Surfactants on the Viscoelastic Properties of Zwitterionic Surfactant Solutions”, Langmuir, 8, 2140-2146 (1992); and Hoffmann et al., The Rheological Behaviour of Different Viscoelastic Surfactant Solutions, Tenside Surf. Det., 31, 389-400, 1994. Viscoelasticity is caused by a different type of micelle formation than the usual spherical micelles formed by most surfactants. Viscoelastic surfactant fluids form worm-like, rod-like or cylindrical micelles in solution. The formation of long, cylindrical micelles creates useful rheological properties. The viscoelastic surfactant solution exhibits shear thinning behavior, and remains stable despite repeated high shear applications. By comparison, the typical polymeric thickener will irreversibly degrade when subjected to high shear.
One can see that is would be highly desirable to have viscoelastic cleaning composition. Thus there is a need in the art for cleaning compositions with cleaning capabilities where the composition has the desired viscosity for sufficient contact time, but without the other deficiencies of presently available polymer based thickeners.
Accordingly it is an object herein to provide a cleaning composition that includes a viscoelastic surfactant.
It is yet another object of the invention to provide a cleaning composition with a thickening agent that can also impart a cleaning function to the composition.
It is yet another object of the invention to provide a cleaning composition using a viscoelastic surfactant that can be formulated as either an acidic, neutral or caustic cleaner.
It is yet another object of the invention to provide a cleaning composition using a viscoelastic surfactant that has better cling and reduced misting than typical cleaners which employ polymer based thickeners.
It is yet another object of the invention to provide a cleaning composition that is safe, environmentally friendly and economically feasible.
Other objects, aspects and advantages of this invention will be apparent to one skilled in the art in view of the following disclosure, the drawings, and the appended claims.